Avoid use of fragile Swing classes in tests (for compatibility with JDK 8u40)

Issue: SPR-12235
(cherry picked from commit a80495b)
Remove outdated references to ContextLoaderServlet

Issue: SPR-7725
(cherry picked from commit 94e26fd)
Defensively use setRemoveOnCancelPolicy for JDK 6 compatibility

Issue: SPR-12238
(cherry picked from commit e003d21)
LiveBeansView escapes double quotes in resource descriptions

Issue: SPR-12252
(cherry picked from commit 92f7121)
WebAsyncManager avoids concurrentResult.toString() and builds correct DeferredResultProcessingInterceptor keys

Issue: SPR-12253
(cherry picked from commit bf99d6a)
Tracking ASM 5.0.4 development: Fix for ASM issue 317539

Issue: SPR-12255
(cherry picked from commit e8486e2)
Update default SockJS CDN location

This commit updates the default location of the SockJS' client library.
The previous location is being retired by the project maintainers.

The new default location is backed by several CDN providers:
* https://cdn.jsdelivr.net/sockjs/0.3.4/sockjs.min.js

See sockjs/sockjs-client#198

Issue: SPR-12254
(cherry picked from commit a6e1c53)
Deprecated BeanDefinitionDocumentReader's setEnvironment method in favor of access via XmlReaderContext

Issue: SPR-12248
Polishing